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parport(3hal) HAL parport(3hal)


hal_parport - portable access to PC-style parallel ports


#include "hal_parport.h"

int hal_parport_get(int comp_id, hal_parport_t *port, unsigned short base, unsigned short base_hi, unsigned int modes)

void hal_parport_release(hal_parport_t *port)


A HAL component identifier returned by an earlier call to hal_init.
A pointer to a hal_parport_t structure
The base address of the port (if port >= 16) or the linux port number of the port (if port < 16)
The "high" address of the port (location of the ECP registers), 0 to use a probed high address, or -1 to disable the high address
Advise the driver of the desired port modes, from <linux/parport.h>. If a linux-detected port does not provide the requested modes, a warning is printed with rtapi_print_msg. This does not make the port request fail, because unfortunately, many systems that have working EPP parports are not detected as such by Linux.


hal_parport_get allocates a parallel port for exclusive use of the named HAL component. The port must be released with hal_parport_release before the component exits with hal_exit.


If the port is a parallel port known to Linux, and Linux detected a high I/O address, this value is used. Otherwise, if base+0x400 is not registered to any device, it is used. Otherwise, no address is used. If no high address is detected, port->base_hi is 0.


typedef struct

unsigned short base;
unsigned short base_hi;
.... // and further unspecified fields } hal_parport_t;


hal_parport_get returns a HAL status code. On success, port is filled out with information about the allocated port. On failure, the contents of port are undefined except that it is safe (but not required) to pass this port to hal_parport_release.

hal_parport_release does not return a value. It always succeeds.


In new code, prefer use of rtapi_parport to hal_parport.

2006-10-12 LinuxCNC Documentation